The invention relates to a tooth brush with a replaceable bristle insert that can be snapped into an oblong mounting recess of a head part of the handle of the tooth brush. A release button of the bristle insert extends through an opening in the top wall of the mounting recess. Locking strips protrude from the bristle insert which engage in corresponding locking grooves formed in the mounting recess.
Tooth brushes of this kind, which are also called changeable head tooth brushes, are known in numerous embodiments. It is common for the connection between the bristle insert and the head part to take place via a locking connection. Desirably, the bristle insert should be anchored tightly in the head part when the tooth brush is used, so that it cannot be loosened unintentionally. Also, the locking connection should be easily releasable so that the bristle insert can be changed in a simple way without using any tools. In one known tooth brush (described in DE-GM 91 09 625), the bristle insert is shaped such that its side walls converge in the direction of the bristles. These side walls and the corresponding inner walls of the mounting recess are smooth and free of grooves. However, opposing front and rear ends of the insert are provided with locking connections formed by locking strips or locking protrusions which mate with locking grooves formed at ends of the recess. Since this locking connection engages at both ends of the bristle insert near to its outer surface on the bristle side, there is the danger that the locking connection might disengage on one end of the bristle insert and the bristle insert would be released from the head part when the head part is deformed. To avoid this, a relatively large undercut must be provided in particular on the locking connection of the handle to guarantee an interlocking mounting engagement. This has, on the other hand, the consequence that a relatively large deformation and thus a large force is required for releasing the bristle insert.
In another known tooth brush (described in DE-OS 30 38 895), locking strips are arranged on the side surfaces of the bristle insert in parallel and spaced relationship. Since the surrounding surface of the bristle insert runs along the entire perimeter perpendicular to the base surface of the bristle insert on the bristle side, the connection between the bristle insert and the head part takes place without a clamping action, i.e. only through the locking force being imposed on the locking strips.
Also, in a tooth brush of the type described in DE-PS 37 24 640, the peripheral surface of the bristle insert extends perpendicular to the base surface of the bristle insert, i.e., the base surface from which the bristles protrude. The anchoring of the bristle insert takes place exclusively by means of mounting strips, which extend for this purpose over a significant portion of the length of parallel side surfaces of the bristle insert. A locking groove accepting the locking strips extends around the entire inner perimeter of the mounting recess through which the contact surfaces are further reduced between the peripheral surface of the bristle insert and the mounting recess.